<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <meta http-equiv="X-UA-Compatible" content="ie=edge">
    <title>Document</title>
</head>
<body>
    <script>
        // && || !
        /* 
            &&两边为true才是true
            ||一边为true就是true
            ！ 取反
         */
    
    </script>
</body>
</html>